2.5 - 3" will i benefit

hi all,

i currently have a 3inch downpipe from my gt40088 bi=ut at the join my exhause is 2.5 diamiter pipe.

my turbo dose not come onto full boost until 4000 rpm.

will i benefit from fitting a full 3 " system from the downpipe. i have baught it but i dont want to fit it if there will be no rear improvement from it.

will my tubby spool faster? and i was told the ability to clear faster will allow my egt to cool faster?

all comments apriciated.

Your catback shouldnt be smaller than your downpipe as it create's restriction which is BAD! You want a 3" on there to let it breathe properly

interesting question, i have a similiar problem.. single turbo but my decat 2.5" and everything else is 3"

thanks martin the 3 inch shall be fitted .

Yes, you should really be using a 3inch 2nd pipe with a single turbo, especially if your DP is already 3 inch. My old 2.5inch 2nd pipe was a restriction, not for the spool, but at high rpm's it was casuing a restriction. After changing to a 3 inch it performed a little better at high rpm.

In which gear is it "coming in at 4k"? How much boost and is "coming in" considered maximum boost?

well it hits full boost 8psi at 4k in 3rd gear. by coming in i mean it kind of goes from vacume to full boost straight away at 3.9-4k

if that makes sence. i know the map iss all wrong so thats probably the reason for this

I had a 2.5 decat pipe in my exhaust with a GT4088 and i could make 1.3bar by 3,800RPM and it made very good power and torque, so i doubt 0.5" will make a big difference, unless you are going for a drag setup or very high power where every little thing will have an impact.

I had a 2.5 decat pipe in my exhaust with a GT4088 and i could make 1.3bar by 3,800RPM and it made very good power and torque, so i doubt 0.5" will make a big difference, unless you are going for a drag setup or very high power where every little thing will have an impact.

no im not . its being mapped by ryan on the weekend so ill put it on before then just to be on the safe side , it wont hurt to have a slighty freer flowing pipe will it ?